Alternating-current source



May 20, 1924. 1,494,935

' E. O. SCRIVEN ALTERNAT ING CURRENT S OURCE Filed July 16 1918 y WWW Patented May 20; 1924.

UNITED STATES 1,494,935 PATENT OFFICE.

EDWARD O. SGRIVEN, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC OOM- PANY, INCORPORATED, OF NEW YORK, N. Y. A CORPORATION OF NEW YORK.

ALTnnNA'rINe-cURnnNT SOURCE. Application filed m is, 1918. Serial No. 245,140.

To all whom it may concern:

Be it known that I, EDWAR O. SQRIVEN, a citizen of the United States, residin at New York, in the county of New ork,

State of New York, have invented certain new and useful Improvements in Alternating-Current Sources, of which the following is a full, clear, concise, and exact description.

Thisinventionrelates to alternating current sources of the electron discharge type.

More particularly this invention relates to oscillators of the electron discharge type, in which the .frequency of the oscillations generated is governed by a tuned oscillation circuit, the natural frequency of which ma be varied. I

n object of the invention is to provide an oscillator which will generate substantially pure sine Waves.

Another object of the invention is to provide an oscillator of the electron discharge type having coupled output and input circuits, with means for preventing harmonic frequency oscillations from being fed back to the input circuit.

A further object of the invention is to provide means for varying the tuning of the frequency governing circuit of an electron discharge oscillator without materially varying the feed-back coupling.

A still further object is to provide an oscillator having a frequency governing circuit in which the natural period may be va' ried by chan ing either the capacity or the inductance o the circuit.

Still other objects and advantages of the invention will appear from the following detailed description, taken in connection with the drawing, in which Fig. lvrepresents diagrammatically the circuit arrangements of an oscillator; and Fig. 2 .illustrates a modification of the tuned circuit of Fig. 1.

Referrin to the drawing, an evacuated electron re ay or discharge device 1 includes a constantly active source 2 of electrons, preferably a hot filament cathode, a plate electrode or anode 3, and a' rid or 1mpedance varying element 4. I athode 2 is maintained electronically active by a source 5 of heating current connected to its te'rminals through a variable resistance 6 for regulating the temperature of the cathode.

The grid-cathode or input circuit includes a coupling or secondary winding 7 and may also include a source 8 for determining the normal potential of grid 4 with respect to the cathode 2, and in consequence, the normal impedance offered to electron discharge current between electrodes 2 and 3, although this source is not ordinarily necessary.

The output or plate-filament circuit includes aspace. current branch and a divided path oscillation current branch, this latter branch having a feed-back winding and a frequency determining oscillation circuit in parallel. The space current branch includes a source of space current 9, a choke coil 10, and a variable high resistance 11, the function of which will appear later. The frequency determining oscillation circuit includes a variable capacity12 and a variable inductance 13, which may be an ordinary variable air core inductance as indicated in Fig. 2, but which for low frequency oscillations, requiring oscillation circuits of large natural period, is preferably'wound upon a toroidal magnetic core in order to reduce the size of the elementnecessary to give the required inductance. In parallel with the oscillation circuit is a winding 14, inductively related to winding 7. In series with winding 14' and the oscillation circuit is a blocking capacity 15, the function of which is to prevent local flow of unidirectional current from source 9 through elements 13 and 14. Conductors 16 and 17 connected to the terminals of winding 7 serve-as output connections for the oscillator, element 7 being in effect an autotransformer. Conductors 16 and 17 are preferably connected to the load circuit through a high impedance element in order to prevent undesirable reactions on the oscillator through winding 7, which would otherwise vary the frequency of the oscillations generated. Such an impedance element may be a three-electrode vacuum tube amplifier or repeater such as element 18 to the output circuit of which a load circuit 19 is connected. Obviously any other form of highimpedance may be "employed.

If the closed oscillation circuit 12, 15:! be disturbed electrically oscillations will be set up of approximately the natural frequenc of the circuit. Without the amplifying e fect of the electron. discharge device 1 these would soon be damped out. By virtue of transformer 14, 7, these oscillations set up an alternating otential between the input elements 2 an 4 of the discharge device. This alternating potential is of the frequency of the oscillations set up in circuit 12, 13, and if the winding 7 be coupled in the proper manner to winding 14, it will be of such phase that the change it produces in the space current will reinforce the oscillations in the oscillation circuit. For sustained oscillations, this increased oscillation current must just ofiset the normal decrease due to the damping of the system. The operational characteristics of the dischar e device being a function of the magnitu e of the alternating current in it, the latter adjusts itself to meet this condition. In this manner oscillations having a frequency which is determined by the constants of the tuned circuit are set up. The natural frequency of this tuned circuit may be changed by varying the capacity 12 or inductance 13, thus permittinga change in the frequency of the oscillations generated.

Choke coil 10 excludes all oscillation current components from the path including the space current source. Circuit 12, 13 is tuned to the desired frequency and offers a substantially infinite impedance to currents of this frequency, which will therefore traverse the path followed by winding 14: and condenser 15. Winding 14 ofi'ers high impedance to high frequency currents such as the harmonics usually present in systems of this character, while the branches 12,13 of the tuned circuit ofi'er a relatively low impedance, thus shunting out these undesired components and preventing feed-back of such frequencies to input winding 7 The electron relay may, in one sense, be considered as a reamplifying device for currents of one frequency only. For this reason the device operates to generate relatively powerful fundamental oscillations with weak harmonics. The wave filter which must ordinarilybe provided with oscillators to eliminate harmonics where a pure fundamental frequency current is desired is ordinarily unnecessary with the circuit arrangement just "described.

The characteristic curve plotted between space voltage and space current of evacuated electron discharge devices is, in general, nonlinear, and accordingly changes in voltage of the source 9 produce larger changes in the space current. Changes of the space current or of the impedance between the output electrodes may cause changes in the frequency of the oscillations generated.

Resistance 11 has a substantially linear im' edance characteristic and the series imp'e ance of tubel and resistance 11 is therefore much more nearly linear than is that of tube 1 alone. In consequence of this stabilizing action of resistance 11 there is little tendency for changes in frequency to occur for the reason that the current furnished by source 9 can vary only slightly.

lit it is desired to change the frequency of the oscillations generated, either capaclty aeeaeae 12 or inductance 13 or both may be varied without afi'ecting the feed-backcoupling or varying the impedance presented to space current in the space current circuit. Since inductance winding 13 is not traversed by unidirectional current, the magnetic core may. be operated over a wide range without approaching magnetic saturation.

While the invention has been illustrated and described in connection with a particular form of circuit arrangement it is to be understood that it is not to be limited thereto but only by the scope of the appended claims. I

What is claimed is:

1. In an oscillator, an electron discharge device having an input circuit and an output circuit, said output circuit having means to feed back energy oscillations of a given frequency to said input circuit, and additional means for substantially reventin the feeding back of energy osci lations 0 other frequencies.

2. In an oscillator, an electron relay having an input circuit and a output circuit, said output circuit comprising a closed tuned circuit and -a high frequency path in shunt to said tuned circuit.

3. In an oscillator, an. electron relay having an input circuit and an output circuit, said output circuit comprising a closed tuned circuit, and a high frequency path coupled to said input circuit in shunt to said tuned circuit.

4. In an oscillator, an electron discharge device having an input circuit and a divided output circuit, one branch of which is coupled to said in ut circuit'and another branch of which inc udes a circuit tuned to the frequency of the oscillations generated.

5. An oscillator comprising an electron relay having aninput circuit and a divided output circuit, onebranch of said output circuithaving a lower'impedance than the remainder of the divided circuit for currents of the frequency generated by said oscillator and having a higher impedance than the remainder of the divided circuit for currents of other frequencies.

' 6. An oscillator comprising an electron discharge device having an input circuit and an output circuit, said output circuit comprising a closed tuned circuit and a high frequency path inshunt thereto, and means for varying the natural period of said tuned circuit.

7. In a oscillator, an electron discharge device having an input circuit and an output circuit, means coupling said output circuit to said input circuit, and means shunting said coupling means to divert therefrom substantially all currents except those of the frequency generated by said oscillator.

8. An electron relay having input and outputfeircuits, means to feed back energy of reac es oscillation/currents of one frequency from said output circuit to said input circuit, whereby said oscillation currents may be amplified, and means to prevent the feedback of energy of other frequency currents.

9. In an oscillator, an electron discharge device having, an impedance varying element, space current electrodes and an outmeans to feed back oscillations of a given frequency to said input circuit, and additional means for substantially preventing the feeding back of energy oscillations of other frequencies.

11. An oscillator comprising an electron discharge device having input and output circuits, said output circuit comprising a plurality of branches, means to exclude variation currents from one branch,

means to exclude from a second branch cur rents of the frequency which are produced by the oscillator,'and means coupling a third branch to said input circuit. Y

12. A discharge device comprising a cathode and an anode and a branched circuit connected to said cathode and anode for generating oscillations, one branch of said circuit including in series-a source of electromotive, force, a high resistance element, and an element offering high impedance to variable current, a second branch of said circuit including a closed loop tuned to sub- Stantially the frequency of the oscillations to be generated, a work circuit, and means in said branched circuit but external to said tuned loop for connecting said branched circuit in energy transfer relation to said work circuit. 7

13. An oscillator comprising. an electron discharge device having input and output circuits, means coupling said circuits, and means comprising an anti-resonant circuit connected in parallel with said coupling means for determining the frequency of the oscillations generated independently of said coupling means.

14. An oscillator comprising an electron discharge device having input and output circuits, a transformer for coupling said circuits, and means comprising an anti-reso nant clrcuit connected in parallel with a winding of said transformer for determining the frequency of the oscillations generated independently of said transformer winding.

15. An oscillator comprising an electron discharge device having input and output circuits, aparallel tuned circuit associated therewith for determinin the frequency of the oscillations generate and means connected in parallel to said tuned circuit for coupling said input circuit with said output circuit.

. .16. In an oscillator, an electron discharge device having an input circuit and a divided output circuit one branchl of which is coupled to said input circuit and another branchof which includes a closed circuit tuned to the frequency of the oscillations generated.

17. In an oscillator, an electron discharge device having a cathode,, an anode, and an impedance controlling element, an input cir-.

cuit connecting sa'id'cathode and impedance controlling element, a divided cathode anode circuit having two parallel portions, one of said portions being coupled to said input circuit, and the other of said portions being tuned to substantially independently determine the frequency 'of the oscillations generated.

18. In an oscillator, an electron relay having an input circuit and an output circuit,

. said output'circuit comprising an anti-reso nant circuit, a highfrequency path in shunt to said anti-resonant circuit, and another path in shunt to said anti-resonant circuit including in series a source of electromotive' force, a highresistance element and an element ofl'erlng high impedance to variable current. 1

19. An oscillator comprising an electron discharge device having input and output circuits, said output clrcuit com rising a plurality of branches, means to exc ude variati'on currents from one branch, means to exclude from a second branch currents of the frequency which are produced by the -oscillator, means coupling a third branch to said input circuit, and a high resistance element connected in series with said firstinentioned branch only.

20. A discharge device comprising a cathode and an anode, abranched circuit connected to said anode and cathode, one branch of said circuit including in series .a

source of electromotive force, a high resist ance element, and an element ofiermg' high impedance to variable current, a second branch of said circuit including aclosed tuned loop, a work circuit, and means in athird branch of said branched circuit for connecting said branched circuit to said work circuit. p

In witness whereof, I hereunto subscribe my name this 8th day of July, A. D, 1918.

EDWARD O- SCRIVEN- 

